Biomaterials often exhibit properties that can have utility in a wide variety of applications. The metabolic functionality of biomaterials can have extensive applications in biotechnology (e.g. biosensing, biocatalysis, bioremediation, and bioreactors), medicine (e.g. regenerative medicine, tissue engineering, and recombinant protein production), and in new hybrid materials with improved functional and structural properties. One example of a useful property exhibited by biomaterials is the catalytic activity exhibited by enzymes. For example, the catalytic activity of enzymes can be useful for chemical transformations on a small-scale in a chemistry lab, in large-scale industrial chemical manufacturing or purification operations, in agricultural settings, in food products, and in water treatment.
Biomaterials are frequently difficult to utilize in their natural state. The useful applications described above are difficult to achieve without some way to immobilize the biomaterial. Without immobilization, enzymes with a useful activity or microorganisms that express an enzyme with useful activity can be easily washed away from a desired site of application. Immobilization can allow repeated use without requiring separation and purification of the enzyme or addition of new catalysts. However, to enable practical application of their useful activities, successful immobilization of microorganisms depends on a highly biocompatible encapsulation material of sufficient mechanical robustness that permits the entry of small molecules such as O2, nutrients, electrolytes, and exit of toxic metabolites, hormones, and other bioactive compounds. While the immobilization of microorganisms has been attempted using various substrates and techniques, traditional materials used for cell encapsulation have limited the development of biotechnology and medical applications due to the instability of the biomaterial over long periods of time. Problems with stability can include limited or no catalytic activity expressed by an immobilized enzyme or by an immobilized microorganism that expresses the particular enzyme. Problems with stability can also sometimes include death of the microorganism, although short- or long-term survival of the microorganism is not always required in all applications. Additionally, the mechanical properties of polymeric synthetic and natural materials used for cell encapsulation can be drastically altered by the metabolically active encapsulated cells.
In the past, many problems have been experienced in immobilization of macromolecules, specifically, microorganisms. For example, when immobilizing microorganisms using silica nanoparticles, the proteins from the microorganisms can be adsorbed into the silica nanoparticles, which can cause denaturation and aggregation of the adsorbed proteins and therefore loss of structure and catalytic activity. Traditional microorganism immobilization protocols can also lead to adsorption and denaturation when temperatures are increased. When encapsulation procedures include hydrolysis or condensation steps, the procedure can require additional steps to remove the byproducts of the hydrolysis or condensation reactions. When encapsulation procedures include the use of colloidal precursors such as sodium or potassium silicate, the removal of the sodium or potassium ions can be required.
Atrazine is a widely used herbicide. As a result, atrazine can be found in soil, groundwater and surface water. There is currently extensive interest in identifying an efficient way to transform atrazine into hydroxyatrazine. Hydroxyatrazine is not regulated, it adsorbs more tightly to soil particle than atrazine, and also degrades more rapidly in the environment. The approaches for atrazine remediation are very diverse and include use of free enzymes (atrazine chlorohydrolase) or the microorganisms that express these enzymes. When enzymes or microorganisms are used they are usually added into the soil to eliminate the contaminants. However, this approach is not practical for water treatment applications. A method that can immobilize microorganisms while maintaining their enzymatic abilities is needed.